PROJECT SUMMARY Electronic cigarette (e-cigarette) use is increasing each year among young adult smokers but more than half of young adult smokers who start using e-cigarettes do not quit smoking, instead they become ?dual users.? While dual use could lead to reduced use of cigarettes, the long-term impact of using e-cigarettes on nicotine dependence, smoking behaviors, and health are unknown. Smoking behavior is generally viewed negatively by others. However, identifying as a ?vaper? (e-cigarette user) provides a more positive social image and allows young adult dual users to distance themselves from a smoker identity. Smoker identity is associated with smoking behavior in young adults. However, there is no research on vaper identity, how smoker and vaper identities influence each other, and how these identities influence smoking and vaping behaviors over time. The Aims of this study are 1) administer 2 online surveys to examine how smoking and vaping behaviors and identities change over 6 months in 18-29 year old young adult smokers who have initiated e-cigarette use in the past 6 months; 2) conduct on-line individual interviews with fifty of the participants who complete the second survey to explore the influence of social identity and social stigma on smoking and vaping behaviors; 3) validate measures of vaper identity and vaping stigma scales in young adult dual users. Young adults (n=500) who regularly smoke cigarettes, identify as a smoker, and initiated e-cigarette use in the past 6 months will be recruited to complete two online surveys 6 months apart. Participants will be recruited through online postings on social media sites popular with young adults including Buzzfeed, theSkimm, Craigslist, and Facebook. Young adults who see the posting and click on the link will answer a series of eligibility questions on a secure website. Eligible participants are then asked if they would be willing to take two online surveys and participate in an online interview if selected. Those who agree will take an online survey and another survey six months later. Eighty percent (n=400) of those who take the first survey are expected to take the second survey. Fifty of the young adults who complete the second survey will be invited to participate in an online interview for a more in-depth discussion of vaping and smoking identities and if/how these changed over 6 months. This study directly addresses FDA research questions #4 dual use, and #9 by examining identity which influences susceptibility to marketing messages. Smokers who have a stronger smoker identity are more susceptible to tobacco industry marketing messages. In this way, the e-cigarette industry can increase susceptibility to e- cigarette marketing messages by targeting young adult vaper identity. These findings will inform FDA regulations on e-cigarette industry marketing messages and practices. Findings can also assist the FDA in developing effective anti-smoking messages for dual users who may no longer identity as smokers to help extinguish smoking.